Manufacture of iron and steel.



a sane FRANKA. N'ILMOT, OF BRIDGEPORT, CONNECTICUT.

MANUFACTURE OF IRON AND STEEL.

No Drawing.

' act description.

- furnace.

My invention relates to the manufacture of steel and is designed to provide an improved method by Which steel may be more cheaply and rapidly produced than heretofore.

The invention generally stated, consists in smelting iron ore in a blast furnace yithout regard to analysis as regards silicon in the pig produced, and preferably also as to sulfur and phosphorus, giving a product relatively high in silicon and preferably also in phosphorus and sulfur. That is, there is no proportioning the charge so as to bring the content of these metalloids Within the proportions required for basic or Bessemer plg. The molten pig metal from a blast furnace or furnaces operated in this manner is taken to a large regenerative tilting furnace of the open hearth type in which a constant pool is maintained. In this mixer, the metal is given a preliminary open hearth treatment, but at a low temperature compared with that of ordi' nary open hearth methods. For example, the temperature may be i000 F. lower than the ordinary temperature of open hearth manufacture, as in the primary furnace described in the United States patent to W. R. Palmer, No. 9249525, granted June 15th, 1909. From this mixer, charges are tapped from time to time, leaving a pool constantly therein, and these charges are taken to make a portion or the whole of a charge for an open hearth furnace of the ordinary type.

In carrying out my invention, I employ one or more blast furnaces, a regenerative tilting mixing furnace, and open hearth furnaces, whose charges are partially or wholly taken from the intermediate large tilting The transfer of metal from the blast furnace to the mixer and from the mixer to the open hearths may be carried out byladles and in the usual Way, or, in any other desirable, manner.

In carrying out the inventiom the blast furnace is charged in the usual manner, excopt that the usual proportioning of the fur- Specificution of Letters Patent.

Patented Dec. 19, 1911.

Application filed January 2 7, 1911. Serial No. 605,015.

'nacc charges, particularly as to limestone and COlCO, is not required, since the percentage of silicon in the pig produced is immaterial. The limestone and fluxes Will remove a part of the metalloids, but there is no proportiouing to keep these mctalloids below a definite maximum content, as now required and universally used in blast furnace practice. On account of thisnon-proportioning or calculating of the flux, the i'amount of limestone and coke may be, and preferably is, materially reduced below the amount normally used in blast furnace opovations. By this manner of operating the blast furnace, I not only reduce the cost by reducing the amount of limestone and coke in the charge; but I am also enabled to increase the pig iron output of the furnace, since no attention is paid to the content of silicon and the some may be the case as to the phosphorus and sulfur. The molten pig iron thus produced, which is high in silicon, and may be relatively high in phos phorus and sulfur, is tapped preferably from a series of blast furnaces o jierctcd in this manner at successive intervals and taken to the large regenerative tilting furnace and. charged therein. A constant bath of: metal is maintained in this minor, metal being successively charged into this bath from the furnaces, and successive charges of the treated metal being taken out of this mixer for the open hcarths. In this mixer, the metal is mixed tl'filll'tllfi several blast furnaces, if such are employed, and by the use of the regcncimtors, the metal is treated to reduce the amount oi" silicon as Well as sulfur and pl'lOSPlWlllS. This action is carried on at a much lower temperature than that ordinarily used in open hearth treatment and may be about 1000 F. below ordinary steel making temperatures. This mixer is provided with a basic lining and the relatively low telnpe 'ature prevents any appreciable attack from the silicon upon the basic lining. This preliminary treatment partially eliminates the silicon, phosphorus and sulfur, and from the mixer I tap for use in the open hearth furnaces a molten metal which is usually refined to about onediall the percentage of the silicon and a material reduction in the percentage of phosphorus and sulfur present in the standard steel making pi Lime, or basic material or flux may be added to the mixer as required, or flux may be added in the the metallic charge and the operation.

- In tapping the partially refined metal from the mixer, the mixer is preferably tilted to discharge the proper amount into a ladle and this charge is fed into one of the open hearth furnaces and preferably combined therein with low grade material which may include low grade scrap, borings of castiron, turnings of steel, etc., high silicon pig, iron oxids like scale, cinder or iron ore, or any other material containing iron. If the open hearth charge is made up partly of each class of material, the solid material is preferably charged first and brought to a suitable condition and a charge of the partially refined metal from the mixerthen delivered to complete the open hearth charge. The slag in the mixer is preferably not charged into the open hearth as it will be considerably exhausted. In tapping the open hearth after the usual heat, which, however, may be shortened on account of the preliminary treatment in the mixer and the more violent reaction in charging molten but partially refined iron or semi steel into the heated, partially melted or molten charge already in the finishing open hearth and which conditions are regulated to secure the proper degree of instantaneous reaction or boiling to insure the desired or best and most economical number of heats per week; the open hearth slag may be charged back into the mixer to assist in removing or absorbing the metalloids and impurities. This slag will be charged in a molten condition and will aid in protecting the basic lining from' oxidation and also in. protecting the furnace bottom in the mixer. These operations proceed continuously, the open hearth furnaces being tapped when the heat is finished, fresh charges placed therein and made up either from a mixture of solid material with partially refined mixer metal or from the latter alone, while charges of the high silicon molten pig are fed from time to time to the mixer in which the pool of partially refined metal is maintained.

The main feature of my invention therefore resides in the triplex process above described, wherein the blast furnace is run at the mmlmum cost for producing pig ironregardless of analysis, while the regenerative mixer partially refines this low grade pig at a relatively low cost for fuel and furnace maintenance owing to the low heat or tem- "perature required and partially removes the silicon which the slag readily absorbs even at the low temperature present. At this temperature the silicon as an acid is not so active as to readily attack the basic lining,

while the slag also removes a considerable amount of phosphorous and sulfur, thus preparing the metal for the open hearth finishing furnaces in which the metal is finished into steel, either with or without partial charges of other materials, such as low grade scrap, borings, turnings, etc.

The advantages of my invention will be apparent to those skilled in the art. The processenables a blast furnace to be run with maximum economy and production giving a pig iron in which no attention is paid to the amount of silicon, sulfur and phosphorus contained. On account of the non-proportioning or calculating of the charges in the usual way, the amount of limestone and coke in the blast furnace charge may be reduced and the output of I pig iron lncreased. The time used in the open hearth heats may be considerably reduced on account of the preliminary par tially refining inv the tilting open hearth or mixing furnace; and low grade material,.

such as a poor grade of scrap and cast iron bormgs, turmngs, etc., may be worked up in the open hearth furnaces 1n conJunctmn with the partially refined molten pig and.

steel of the finest analysis and soundness produced. Such steel may be made suitable for deep stamping work, also the substantially acid proof, so called, ingot iron and similar steels, as Well 'asthe higher carbon and alloy steel used in the manufacture of springs, forgings and the like. This process also gives advantages in the production of steel from a chromium nickel iron ore,

By the extra such as certain Cuban ores. fiuxing of this process the chromium can be reduced to one-half or one-third per cent, this producing fine steel for rails, stampings, forgings, etc., with but a fraction of the metallic loss in the direct blast furnace and Bessemer blowing followed by the basic open hearth method-in other words the duplex process. A triplex system is thus afforded lbs which is of advantage both in smelting in the blast furnace and in reduction of time in the open hearth. The metalloids, such as silicon, phosphorus and sulfur are reduced and partially eliminated in the preliminary mixing furnace in which the basic lining I and lime conditions, if used, act forthis purpose. The low temperature avoids attacking the lining in such case.

Many variations may be made in the form and arrangement of the apparatus without departing from my invention.

I claim:

1. In the manufacture of steel the steps consisting of smelting iron ore without reference to analysis for silicon content of the pig to produce a low grade pig, treating said pig in a basic regenerative open hearth at a temperature materially belownormal steel making temperatures to partially eliminate the metalloids, and then transferring the metal to and treating it in an open hearth furnace to produce steel.

2. In the manufacture of steel the steps consisting'in smelting iron ore in a series of blast furnaces without regard to silicon analysis, supplying molten pig from the series of blast furnaces to a regenerative open hearth furnace, maintaining a constant pool therein, treating the metal therein to reduce the metalloids at a temperature materially below ordinary steel making temperatures, and transferring charges from said furnace from time to time to open hearths to finish into steel. r

3. In the manufacture of steel the steps consisting of smelting iron ore to produce a low grade pig without reference to metalloid analysis, and treating said pig in a regenerative open hearth furnace to partially eliminate the silicon, phosphorus and sulfur preliminary to further treatment.

4. In the manufacture of steel the steps consisting of smelting the ore with limestone materially below the normal amount in blast furnace production of basic pig, partially eliminating the metalloids in a preliminary basic furnace at a temperature materially below regenerative steel making 5. In the manufacture of steel the steps consisting of smelting iron ore with a burden of limestone and coke materially below their normal burden in producing basic ig from similar ores, partially eliminating t e metalloids in a preliminary basic furnace at a temperature materially below ordinary steel making temperatures, and transferring said partially refined metal to an open hearth furnace for reduction into steel.

6. In the manufacture of steel the steps consistim of mixing the molten pi metal from difierent sources in a basic irnace, maintaining a pool therein, treating said metal at a temperatu e materially below normal steel making temperatures to partially eliminate the metalloids, and transferring charges of said partially refined metal from time to time to open hearth furnaces.

In testimony whereof, I have hereunto set my hand.

FRANK A. WILMOT.

Witnesses C. D. S. MILLER, R. C. WILMOT. 

